The overall purpose of the conference is to provide a forum for the critical exchange of ideas, information and expertise in the area of nonventilatory functions and properties of the lung. The topics chosen represent: 1) Areas which are felt to be important for our eventual understanding of lung function and its response to damage but which are now somewhat neglected, and 2) Areas undergoing rapid and important increases in knowledge. The topics include: 1) Mesenchymal-epithelial interactions, 2) Turnover of macromolecules and membranes, 3) Endothelial cells, and 4) Pulmonary surfactant. The overall theme of the conference is regulatory processes in the lung and its cells. This represents the third Gordon Conference on nonventilatory functions of the lung. The first two were outstanding successes; 62 scientists attended the first and 100 attended the second conference. It seems to be developing into a continuing focus of communication and espirit among workers in this field, like many other Gordon Research Conferences.